Background: This project is prompted by the urgent public health need to prevent and treat obesity and obesity-related metabolic diseases in Hispanic and African American adolescents, ethnicities especially prone to obesity and future obesity-related co-morbidities. Objectives: (1) To determine the efficacy and dose-response effects of a 16-wk program (2x/wk or 4x/wk) on insulin sensitivity, body fat and ectopic fat (visceral, liver, muscle and pancreatic fat), atherosclerosis progression and cardiovascular disease risk factors; (2) To determine if improvements in any occurring ectopic fat depot (visceral, muscle, liver or pancreas) is related to improvements in risk factors for type 2 diabetes and cardiovascular disease; 3) To determine if improvements in Q-IMT are related to reductions in cardiovascular risk factors; and 4) To determine differences with ethnicity cross-sectionally and in response to the exercise intervention. Methods: Hispanic and African Amercian obese adolescents will be randomly assigned to control, 2 days/wk or 4 days/wk study groups. Dependent variables include insulin sensitivity and beta-cell function by IV glucose tolerance test; whole body composition and ectopic fat by DEXA, magnetic resonance imaging and spectroscopy, carotid thickness by ultrasonography (including determination of lesions and plaque vulnerability), and cardiovascular risk mediators: oxidative stress (8-isoprostane PGF2alpha, oxidized LDL and myeloperoxidase), systemic inflammation [C-reactive protein (CRP)], monocyte attraction [monocyte chemotactic protein-1 (MCP-1)], monocyte adhesion [intracellular adhesion molecule-1 (slCAM-1)], and the plaque stability marker [matrix metalloproteinase-9 (MMP-9)]. Significance: This project will for the first time determine in adolescents of any ethnicity the efficacy and dose-response effects of progressive resistance exercise on multiple risk factors for obesity-related disease risk. The outcome will determine if the underlying metabolic and atherosclerotic disease processes that commonly begin in childhood are modifiable with resistance exercise, independent of intentional weight loss, in growing adolescents, and determine if there are ethnic differences in response to this type of intervention. Furthermore, if the hypotheses are supported, greater emphasis may be placed on the pivotal role of resistance exercise as a therapeutic intervention to reduce future type 2 diabetes and cardiovascular disease risk in minority adolescents.